1. Field of the Invention
This invention relates to a safety device for an oil burner, and more particularly to a safety device for an oil burner which is adapted to monitor combustion of the oil burner utilizing rectification due to flame formed by the combustion.
2. Description of the Prior Art
Conventionally, the detection of excessive flame due to abnormal combustion in an oil burner has been typically carried out by means of a high limit switch. This is adapted to detect abnormal rise in temperature of a heat exchanger or a frame. However, such abnormal temperature rise occurs as a result of abnormal combustion, accordingly, the prior art fails to detect starting of the abnormal combustion. In view of such a defect of the prior art, a flame detecting apparatus for detecting abnormal combustion in an oil burner was proposed, as disclosed in Japanese Utility Model Application No. 163756/1982. More particularly, the apparatus proposed is provided with two combustion flame detectors each utilizing the rectification of flame, one of which is adapted to detect flame sufficiently small to be blown out and the other is adapted to detect only excessive flame formed due to abnormal combustion.
However, the arrangement of such two flame detecting devices is highly disadvantageous from viewpoints of its structure and cost.
Accordingly, it would be highly desirable to provide a safety device for an oil burner which is capable of detecting not only small flame due to abnormal combustion but excessive flame by means of a single flame detector.